i want to build a propane forge but im not really sure about the best way to insulate it.  whether to use fire brick, insulated refractory brick, refractory board, kaowool ?  there are so many differant options that i dont know which way to go.  i mostly make small stock reduction knives but would like to move onto forging now.  a forge 8" square and 12" deep would be plenty big.  just wanna make sure i build it right the first time so if i ever decide to weld in it i can.  any and all advice is more than welcome.  id love to buy a lil johny forge but cant afford it so ill fire up the welder and get dirty.

Kaowool is my preference. Cheap, easy to work with & very effective. It also has the benefit of letting you ' tune' the internal dimensions of your forge to get the most efficient size for your burner. As you reduce the internal dimensions of the forge, you increase the temperature, letting you set up for simple quenching use (for stock reduction work), basic hot forging & welding, simply by adding or removing wool as necessary. Once you get the feel for it, you'll settle on one size for everything.
I have 4" of kaowool in my farrier's forge & it's lasted 4 years now.

Kaowool, Satanite coating, with ITC over the Satanite.

I built a horizontal forge out of an old propane cylinder.  Lining it with Kaowool was the easiest thing for me-I put some thin fire bricks in the bottom first wrapped the blanket from edge to edge. Cut holes in the blanket for your burners and there you have it.  Like Rob mentioned, I've also used some Kaowool scraps to make the interior smaller at times.  I started out with refractory cement coating my Kaowool and HIGHLY recommend ITC 100.  When I got a few more $'s I got the latter and put over the former-I can now reach forge welding temps.  There are several posts of different forges built on this site-try a search too and you may get some other good ideas.

Good luck-there's just nothing like beating on hot steel   .

Jeremy

yea i have 24 fire bricks that ive made a small forge in the driveway with and seems to work good the burner is an old lead smelting pot burner and gets pretty hot but uses alot of propane  to keep temps high.  seems that the fire bricks that came out of a boiler do ok but dont keep as much of the heat in as id like.  maybe kao wool with itc-100 on it and a fire brick floor would be good and easy to make.  another thing i was woundering is that if the zoller forge z burners are any good id rather buy a burner that i know will put off good btu's right from the get go.  or should i use air forced to get up to welding temps?